Rich, Jim, Seb, Fabrice
We can only see this noise line when the sensor correction is ON, so we have been chaising it in the the sensor correction channels, but could not find anything.
We are back to noise hunting in the ISI channels.
- The first plot attached shows ASDs with sensor correction ON (2 nights ago). The amplitude of the peak is 2.5e-8 m/Hz^0.5
- The second plot shows ASDs with sensor correction OFF (last night). The amplitude is 8e-9 m/Hz^0.5. No visible noise line...
We are getting the ISI local sensors data on HAM2 and HAM3 with the sensor correction OFF, to perform signal subtraction, and see if the noise line could be burried in the seismic signal (and somehow amplified by the sensor correction?)
I did the subtraction between HAM2 and HAM3 ISI channels. I have attached the cartesian results for Z, which was the most interesting. The first plot attached is with sensor correction ON. The second plot attached is with sensor correction OFF. The residual with sensor correction OFF shows nothing at 0.66 Hz.
It might worth to have another look at the coherence between the output of the FIR filters of HAM2 and HAM3 (someone one site will have to do it, I can't access those remotely, thanks)
